Prefabricated double wall concrete components have been used in the past to construct building walls. Such wall members may include a plurality of welded wire spacing frames to retain the slabs of the wall member in a spaced apart configuration. Typically, the welded wire spacing frames provide limited structural reinforcement of the wall member. It has been proposed to use such prefabricated wall members as structural flooring and/or roofing members. However, a dual slab member designed as a wall may not be readily adaptable to a floor or roofing application due to different loading forces on the member. For example, a wall member used in a floor application may have a limited span distance due to the minimum structural capacity provided by the welded wire spacing frames. More robust welded steel trusses having upper and lower longitudinal portions embedded in respective upper and lower slabs have been proposed as a framing structure for a composite truss that can span up to 60 feet and greater. However, the great weight of these large dual panel prefabricated trusses raises problems of lifting and moving the a truss without damaging the truss panels. It becomes desirable to incorporate means in a truss during manufacture of the truss for connecting lifting cables or hooks which can support the great weight of the truss. Attachment techniques used in the manufacture of such framing structures significantly adds to the cost and time needed to manufacture the trusses and thereby increases the cost of the composite truss.
In our prior U.S. Pat. No. 8,667,755 for a Dual Panel Composite Truss Apparatus, a dual panel truss has a pair of spaced apart prestressed concrete panels having a versatile and adaptive structurally supporting end bearing truss on the ends thereof. The end bearing truss incorporates a versatile and adaptive structural support on each end of the composite truss. The end bearing truss is formed as an integral part of the composite truss for supporting the ends of the composite truss when the composite truss is used for the floors and ceiling of a building. The end bearing truss advantageously forms each end of each concrete panel form for the concrete pour when making each concrete panel. This prior patent is an improvement of our prior U.S. Pat. No. 7,891,150 for a Composite Truss by Robert D. Finfrock and Allen R. Finfrock. In this prior patent, a composite truss has a pair of spaced apart prestressed concrete panels and a plurality of substantially vertical members spanning between the pair of spaced apart concrete panels, one end portion of each vertical member being embedded in one of the spaced apart concrete panels and the opposite end being imbedded in the other concrete panel. The truss includes a diagonal member spanning between the one end of a vertical member and the other end of an adjacent vertical member. Each end of the diagonal member non-structurally engages an end of a vertical member. Each diagonal member also has a length thereof embedded in the concrete in each spaced apart concrete panel. Each end of the composite truss has a prefabricated concrete end bearing beam for supporting the end of the composite truss.
Our prior U.S. Pat. No. 8,763,333 is for a method of making a dual panel composite truss having a pair of spaced apart prestressed concrete panels. The process includes assembling the truss frame, which includes interconnecting and mounting a plurality of steel posts and connecting truss members and reinforcing rods, and positioning the assembled truss frame in a panel form having prestressed strands therein for pouring a first prestressed concrete panel on one side of the truss frame. The truss frame with the first concrete panel is then stripped from the form, lifted and placed on a turning table and turned to position the other side of the truss frame in the panel form for pouring concrete into the panel form for pouring the second prestressed concrete panel.
Care must be taken in lifting the truss frame after curing one concrete panel for placement on the turning table to avoid any damage to the first concrete panel. The dual concrete panel truss does not reach full strength until both concrete panels form the completed composite dual concrete panel truss. This requires all the lifting points for lifting the truss frame having one concrete panel formed thereon to have some force thereon so that the concrete panel is being lifted by all the points to avoid damaging the concrete panel. Once the truss frame having one panel is lifted and placed on a turning table, it is turned to place the truss frame in a mold for forming the second panel of the composite truss.
The present invention is for a truss lifting process and apparatus for coupling a lifting truss to a load to be lifted especially for lifting a large prefabricated concrete panel in the making of a dual panel truss having a pair of spaced apart concrete panels. A lifting truss has a plurality of spaced hydraulic cylinders hanging therefrom with each hydraulic cylinder having a grappling hook attached thereto for attaching to an attachment member on an object to be lifted. The plurality of hydraulic cylinders are actuated simultaneously to pull each coupled grappling hook and attachment member taut and then locked for the lifting truss to lift the attached object.